Software Phase Locked Loop technique for grid-connected wind energy conversion systems

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Accurate and fast detection for phase angle of the generated voltage is important in parallel grid- connected wind energy conversion systems (WECSs) utilizing converter-inverter unites. Software Phase Locked Loop (SPLL) technique was studied here in this project for precisely detecting the phase angle during presence of the 5th and 7th harmonics.

A second-order loop filter design was proposed here as a good trade-off of the filter performance and system stability. Also, this proposed technique is studied under frequency change and generated voltage unbalance conditions. The developed technique is also implemented in a laboratory setup which includes two synchronous generators (SGs: 250 W, 2.2 kW) each driven by a variable speed prime mover (VSPM) to emulate a wind turbine behavior, two 3-phase PWM-based converter-inverter systems, 3-phase line inductors connected between wind generators and converters, and a digital signal processor (DSP TMS320F240).

Three-phase power circuit for the PWM converter

The main electric circuit of the VSI connected to the utility grid

SPLL applied for wind generation converters

Schematic diagram of the overall proposed WECS control system connected to grid

The experimental results confirm the validity of the proposed technique for parallel integrated WECSs. This work has been published for IEEE 12th Workshop on COMPEL2010 conference, vol., no., pp.1-8, 28-30 June 2010.

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